(1) Field of the Invention
The present invention relates to a process for producing perillyl compounds (such as perillyl alcohol; perillyl aldehyde and .alpha.-terpineol) from limonene using Bacillus stearothermophilus. In particular the present invention relates to a process which produces a high production of perillyl alcohol.
(2) Description of Related Art
The monocyclic terpenoid (+) limonene ((R)1-cyclohexen-1-methyl 4-(1-methylethyl)) is an attractive monoterpene starting material for microbial bioconversion to higher value monoterpenes utilized in flavor and perfume applications (Kieslich et al., Transformation of terpenoids. in Progress in essential oil research. XVI. Ernst-Joachin Brunke (Ed.). 367-394 (1986)). (+) Limonene is a common constituent of many essential oils and is the major component in oils derived from citrus product waste peels (Braddock and Cadwallader, Food Technol. 40(2):105-110 (1992)). As a result, it is one of the least expensive and widely available terpenes, and is used directly in a number of food and other applications (Krasnobajew, V., Terpenoids Ch. 4. In "Biotechnology-Biotransformations" Vol 6a. K. Lieslich (Ed.). 98-125. Verlag Chemie, Weinheim (1984)). Useful oxidation products of (+) limonene include perillyl alcohol ((R)1-cyclohexene-1-methanol-4-(1-methylethyl)); perillyl aldehyde ((R)1-cyclohexene-1-carboxaldehyde 4-(1-methylethyl)), and perillic acid ((R)1-cyclohexene-1-carboxylic acid-4-(1-methylethyl)). These are naturally found in low quantities in citrus, lemon grass, and perilla oils, and are utilized as flavorings and as antimicrobial agents in food and pharmaceuticals.
The possibility of microbial conversion of limonene to other monoterpenes of interest has been examined, and bacteria have been isolated which are capable of growth on limonene yielding metabolites such as (+)-.alpha.-terpineol, (+)-limonene-1,2-diol, (+)-perillic acid, and (+)-.beta.-isopopenyl pimelic acid (Cadwallader et al, J. Food Sci. 54:1241-1245 (1989); Dhavlikar et al, Indian J. Biochem. 3:144-157 (1966); and Krasnabajew, V., Terpenoids Ch. 4. In "Biotechnology-Biotransformations" Vol 6a. K. Lieslich (Ed.). 98-125. Verlag chemie, Weinheim (1984)). While these studies are of scientific interest, commercialization of these processes has been thwarted by the multiplicity of conversion products produced, and the low conversion product concentrations due to the toxicity of limonene to most microorganisms.
U.S. Pat. No. 5,110,832 to Chastain et al shows that bacteria, particularly Bacillus are killed by perillyl alcohol. Thus, there is a problem in finding bacteria which will metabolize limonene, in itself inhibiting to the bacteria, to a compound which kills the bacteria.